Computers, fax machines, printers and numerous other electronic devices are routinely connected by communications cables to network equipment and/or to external networks such as the Internet. FIG. 1 illustrates the manner in which a computer 10 may be connected to network equipment 20 using conventional communications plug/jack connections. As shown in FIG. 1, the computer 10 is connected by a patch cord assembly 11 to a communications jack 30 that is mounted in a wall plate 19. The patch cord assembly 11 comprises a cable 12 that contains a plurality of individual conductors and two communications plugs 13, 14. The communications plug 13 is attached to a first end of the cable 12, and the communications plug 14 is attached to the other end of the cable 12. The communications plug 13 is inserted into a communications jack (not pictured in FIG. 1) that is provided in the back of the computer 20, and the communications plug 14 inserts into a plug aperture 32 in the front side of the communications jack 30. The blades of communications plug 14 (which are exposed through the slots 15 on the top surface of communications plug 14) mate with respective contacts 41-48 (see FIG. 2) of the communications jack 30 when the communications plug 14 is inserted into the plug aperture 32. The blades of communications plug 13 similarly mate with respective contacts of the communications jack (not pictured in FIG. 1) that is provided in the back of the computer 10.
The communications jack 30 includes a back-end connection assembly 50 that receives and holds conductors from a cable 60. As shown in FIG. 1, each conductor of cable 60 is individually pressed into a respective one of a plurality of slots provided in the back-end connection assembly 50 to establish mechanical and electrical connection between each conductor of cable 60 and the communications jack 30. The other end of each conductor in cable 60 may be connected to, for example, the network equipment 20. The wall plate 19 is typically mounted on a wall (not shown) of a room or office of, for example, an office building, and the cable 60 typically runs through conduits in the walls and/or ceilings of the building to a computer room in which the network equipment 20 is located. The patch cord assembly 11, the communications jack 30 and the cable 60 provide a plurality of signal transmission paths over which information signals may be communicated between the computer 10 to the network equipment 20.
In most electrical communications systems that are used to interconnect computers, network equipment, fax machines, printers and the like, the information signals are transmitted between devices over a pair of conductors (hereinafter a “differential pair” or simply a “pair”) rather than over a single conductor. The signals transmitted on each conductor of the differential pair have equal magnitudes, but opposite phases, and the information signal is embedded as the voltage difference between the signals carried on the two conductors of the pair. When signals are transmitted over a conductor (e.g., an insulated copper wire) in a communications cable, electrical noise from external sources such as lightning, computer equipment, radio stations, etc. may be picked up by the conductor, degrading the quality of the signal carried by the conductor. When the signal is transmitted over a differential pair of conductors, each conductor in the differential pair often picks up approximately the same amount of noise from these external sources. Because approximately an equal amount of noise is added to the signals carried by both conductors of the differential pair, the information signal is typically not disturbed, as the information signal is extracted by taking the difference of the signals carried on the two conductors of the differential pair; thus the noise signal is cancelled out by the subtraction process.
Currently, high speed communications systems that are used to connect computers and/or other processing devices to local area networks and/or to external networks such as the Internet typically include four differential pairs per communications cable. In such systems, the conductors of the multiple differential pairs are usually bundled together within a single, jacketed cable, and thus necessarily extend in the same direction for some distance. Unfortunately, when multiple differential pairs are bunched closely together, another type of noise referred to as “crosstalk” may arise, which refers to signal energy from a conductor of one differential pair that is picked up by a conductor of another differential pair in the communications system. The induced crosstalk may include both near-end crosstalk (NEXT), which is the crosstalk measured at an input location corresponding to a source at the same location, and far-end crosstalk (FEXT), which is the crosstalk measured at the output location corresponding to a source at the input location. Both types of crosstalk comprise an undesirable noise signal that interferes with the information signal.
FIG. 2 is an exploded perspective view of the communications jack 30 of FIG. 1. As shown in FIG. 2, the communications jack 30 includes a three-piece housing 35, 36, 37. Housing piece 35 defines (at least partly) a plug aperture 32 that is configured to receive a mating communications plug. Housing pieces 36, 37 partially cover and protect a printed circuit board 34. A plurality of jackwire contacts 41-48 are mounted on the printed circuit board 34 so as to extend into the plug aperture 32 from the back of the communications jack 30. However, it will be appreciated that, in other embodiments, some or all of the jackwire contacts 41-48 may extend into the plug aperture 32 from a different direction such as, for example, from the front of the communications jack 30. Each of the jackwire contacts 41-48 terminates into the printed circuit board 34.
The jack 30 further includes a plurality of insulation displacement contacts (“IDCs”) 51-58 that are mounted on the printed circuit board 34. As is well known to those of skill in the art, an IDC is a type of wire connection terminal that may be used to make mechanical and electrical connection to an insulated wire conductor. In the communications jack 30, a plurality of electrically conductive paths (not shown in FIG. 2) are provided on the printed circuit board 34. Typically, each of these electrical conductive paths will comprises one or more traces that are disposed on one or more layers of the printed circuit board 34. If the traces of one of the electrically conductive paths are disposed on multiple layers of the printed circuit board 34, the traces on different layers may be interconnected by conductive vias. Each of the electrically conductive paths may provide an electrical path between a respective one of the jackwire contacts 41-48 and a corresponding one of the IDCs 51-58. Housing piece 36 includes a plurality of pillars that define slots which receive the IDCs 51-58. Each slot defined by the pillars is configured to receive a conductor of a communications cable so that the conductor may be inserted into a slot in a respective one of the IDCs 51-58.
FIG. 3 is a perspective view of the communications jack 30 of FIGS. 1-2 with the communications cable 60 terminated thereto. As shown in FIG. 3, the communications cable 60 includes either insulated conductors 61-68 which are arranged as four differential pairs 71-74. The individual conductors that comprise each differential pair 71-74 are twisted about each other, and all four differential pairs 71-74 are twisted about each other in what is known in the art as a “core twist” (not visible in FIG. 3). The communications cable 60 may also include a separator 69 that separates at least some of the differential pairs 71-74 from other of the differential pairs 71-74, as well as a jacket 70 that encloses and protects the conductors 61-68.
As is also shown in FIG. 3, each of the conductors 61-68 is terminated onto a respective one of the IDCs 51-58. As illustrated in FIG. 2, each IDC 51-58 includes a pair of opposed upwardly extending arms. As shown in FIG. 3, each conductor 61-68 is inserted into the gap between the opposed arms of its corresponding IDC 51-58. The inner edges of the opposed arms cut the insulation on the conductor such that both a mechanical connection and an electrical connection are established between the each conductor 61-68 and its corresponding IDC 51-58. Typically, a technician terminates each conductor 61-68 of cable 60 into the IDCs 51-58 of communications jack 30 by hand at the time that the communications jack 30 is installed in the faceplate 19.